1. Field of the Invention
The present invention relates to a substrate treatment method and a substrate treatment apparatus for cleaning and drying a substrate. Examples of the substrate to be treated include semiconductor wafers, substrates for liquid crystal display devices, substrates for plasma display devices, substrates for FED (Field Emission Display) devices, substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks, and substrates for photo masks.
2. Description of Related Art
In production processes for semiconductor devices and liquid crystal display devices, substrates such as semiconductor wafers and glass substrates for the liquid crystal display devices are generally treated with treatment liquids. More specifically, such a substrate is treated with a chemical agent by supplying the chemical agent to a major surface of the substrate, and then a cleaning process is performed to rinse away the chemical agent from the substrate by supplying deionized water to the major surface of the substrate supplied with the chemical agent (see, for example, JP-A-2003-92280).
After the cleaning process, a drying process is performed on the substrate to remove the deionized water remaining on the substrate and dry the substrate. Exemplary methods for the drying process include an IPA (isopropyl alcohol) vapor drying method, a Marangoni drying method and a Marangoni spin-drying method, in which IPA is used for replacing the deionized water on the substrate with IPA for drying the substrate.
However, the prior art drying methods using IPA often fail to completely dry the substrate. Where a recess such as a hole or a trench having a high aspect ratio is provided in the major surface of the substrate, for example, only deionized water present in an upper portion of the recess of the substrate is replaced with IPA, and deionized water present in a lower portion (bottom portion) of the recess of the substrate is not sufficiently replaced with IPA. Therefore, the deionized water still remains in the bottom portion of the recess of the high aspect ratio even after the drying process. The remaining deionized water may form water marks in the recess, thereby resulting in deterioration of the characteristics of a device to be formed on the substrate.
More specifically, IPA has a lower surface tension than the deionized water and, therefore, more easily enters the recess of the high aspect ratio than the deionized water. However, IPA does not easily mingle with the deionized water. Even if IPA is brought into contact with the deionized water, the deionized water only partly mingles with IPA in an interface between the deionized water and IPA. With the deionized water present in the fine recess of the high aspect ratio, therefore, IPA merely mingles with the deionized water present in the upper portion of the recess, but does not reach the bottom portion of the recess. Therefore, only the deionized water present in the upper portion of the recess is replaced with IPA, and the deionized water present in the bottom portion of the recess remains to result in water marks.